Precursor Ceramics

Structural characterisation of silicon carbonitride ceramics derived from polymeric precursors - Elsevier

Abstract : Polymeric precursors with tailored structures were prepared from functionalised chlorosilanes. Pyrolysis under inert atmospheres led to amorphous Si–C–N–(H) ceramics at 1000°C. Further heat treatment caused the transformation into the thermodynamically stable crystalline phase assemblage. The structural changes associated with crosslinking, pyrolysis and crystallisation were studied by characterising the solid intermediates between 300 and 1600°C applying 29Si and 13C solid state nuclear magnetic resonance (NMR) spectroscopy. In addition, Fourier transformed infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermoanalytical techniques and density measurements were employed. The combination of these methods and the use of polymeric precursors with tailored structures pointed to a correlation of the polymer architecture with the structure of the amorphous ceramic material.

Active-Filler-Controlled Pyrolysis of Preceramic Polymers - Wiley

Abstract : Manufacturing of bulk ceramic components from materials in the system Si-Me-C-N-O (Me=Ti, Cr, V, Mo, Si, B, CrSi2, MoSi2, etc.) from preceramic organosilicon polymers - such as poly(carbosilanes), poly(silazanes), or poly(siloxanes) - has become possible by incorporating reactive filler particles into the liquid or solid polymer precursor. During pyrolytic decomposition of the polymer matrix, the filler particles react with carbon from the polymer precursor or nitrogen from the reaction gas atmosphere to form new (oxy)carbide or (oxy)nitride phases embedded in a nanocrystalline Si-O-C(-N) matrix. The selective expansion encountered in the filler phase reaction can be used to compensate for the polymer shrinkage upon pyrolytic conversion. The formation of a transient pore network between 400° and 1000°C is governed by the polymer decomposition as well as the filler particle reaction kinetics. Thus, the properties of the oxycarbonitride composite materials can be tailored by controlling the microstructures of the polymer-derived matrix phase, the filler network, and the residual porosity. Near-net-shape forming of bulk ceramic components, even with complex geometry, is possible, making novel applications of polymer-derived bulk materials in biomedical, electrical, and mechanical fields highly interesting.

Precursor-derived Covalent Ceramics - Wiley

Abstract : The preparation of ceramic materials from preceramic compounds provides a means for the synthesis of new materials which cannot be obtained by conventional methods. An example is shown in the figure, which shows carbon-fiber-reinforced silicon carbide coated with silicon carbonitride prepared by dip-coating the substrate with a slurry made of polyhydridomethylsilazane and silicon powder. Progress and applicational examples are reviewed.

Polymer Derived Engineering Ceramics : Wiley

Abstract : Engineering ceramics in the system Si–O–C–N–B manufactured from preceramic silicon containing polymers gain in significance with increasing availability of advanced precursor materials such as poly(carbosilane), -(silazane), -(siloxane) or -(borosilazane). While high temperature resistant Si–C and Si–N ceramic fibers are already used to reinforce ceramic matrix composites (CMC) in air- and spacecraft structures, novel products such as coatings, tapes, foams, and complex shaped components for medium and low temperature applications in the fields of energy, environmental, transportation, and communication technologies become more important in the future. Preceramic polymers offer the possibility of using versatile plastic shaping technologies as well as advanced laminated object manufacturing techniques. Properties can be varied in a wide range by tailoring the molecular structure and composition of the precursor polymer and by loading the polymer with intert or reactive filler powders. Partial conversion of the organic polymer into organic/inorganic hybrid materials yields novel materials which exhibit properties between polymers and ceramics.